The present invention relates to an insulated glazing unit (“IGU”) and more particularly to an IGU which includes an electrically controlled internal shade device that controls the intensity and spectral region of light passing through it, providing both energy efficiency and privacy.
Glass windows, skylights, doors, and the like, which are used in buildings and other structures, are known to waste 5% of the total energy consumed in the United States. Residential and commercial building windows permit solar radiation to pass into the interior of the building and cause unwanted heating, particularly during summer months, thus requiring increased use of air conditioning to remove the unwanted heat. Windows also permit heat to leave the interior of the building during winter months, thereby requiring additional heating of the building. The increased use of air conditioning and heating increases the costs of operating the building and causes increased consumption of petroleum products and other non-renewable energy resources in addition to adding to the initial cost of the structure because of the required HVAC capability. The increased consumption of these resources has become particularly critical as for example, supplies of petroleum decrease and the price of petroleum rises. Also, at the same time that this increased consumption has become critical, new constructions of residential and commercial structures incorporate more glass than was used in older construction, thereby further increasing consumption of these non-renewable resources.
A known method of improving the energy efficiency of windows is to use low emissivity (“low e”) glass in IGUs. However, in spite of their widespread use, the wastage of 5% of the total United States energy consumption still remains.
Another concern about prior art IGUs relates to their installation in buildings that are considerably elevated above sea level from where the IGUs were actually constructed. Since the IGU is a sealed unit with an air gap, as it is raised considerably higher from where it was constructed, the outside air pressure becomes significantly lower than the air pressure inside the unit, causing the air inside the unit to create forces on the glass that may make it expand and eventually shatter. The fenestration industry uses pressure equalizing structures inside the IGU such as breather tubes and capillary tubes to alleviate this problem, but they are limited in function. Capillary tubes can shorten the life of the IGU because they eventually allow moisture to penetrate the IGU, and the moisture will eventually condense on the inside glass surfaces.
Another prior art approach to save energy uses an insulated glass (“IG”) window that incorporates one or more functional electronic layers between the two or more sheets of glass of the IG window. The electronic layers are somewhat clear in one electronic state and allow heat and radiation to pass. In the other electronic state, the electronic layers darken or are opaque to reduce the passage of radiation. The materials used, such as liquid crystal layers, electrophoretic layers, suspended particle layers, and/or electrochromic layers, are also used in display devices. The electrochromic layers are the materials most commonly used for such electronic layers. An example of this approach is described in U.S. Pat. No. 6,972,888, titled “Electrochromic Windows and Method of Making the Same” and issued Dec. 6, 2005 to Poll, et al., the disclosure of which is hereby incorporated herein by reference.
Undesirably, IG windows that incorporate smart glass are difficult and costly to manufacture, have a questionable operating life, have undesirable operating temperatures, can have very slow response times, provide incomplete darkening, and increase power consumption for their operation. They are also limited in their ability to provide clear lines of sight for people inside the building.
It is therefore desirable to reduce the passage of heat and radiation through a window or the like in a manner that avoids the tradeoffs and drawbacks of the above known approaches and also achieves these improvements in a mechanism that would be readily acceptable to users of all types. The present inventors are listed on other U.S. patents directed to inventions that are similar in nature to the inventions described herein. Such patents are U.S. Pat. No. 7,645,977 (titled “Low cost dynamic insulated glazing unit” and issued Jan. 12, 2010 to Schlam et al.); U.S. Pat. No. 8,035,075 (titled “Dynamic insulated glazing unit with multiple shutters” and issued Oct. 11, 2011 to Schlam et al.); and U.S. Pat. No. 8,134,112 (titled “Method of fabricating an insulated glazing unit having controllable radiation transmittance” and issued Mar. 13, 2012 to Schlam et al.), the disclosures of which are hereby incorporated herein by reference. The present application is directed to inventions and further improvements regarding the technology of the aforementioned patents.